1. Field of the Invention
The present invention relates to a dishwashing machine, more particularly to an improvement of a dishwashing machine wherein the racked dishes are washed and rinsed by spray of hot water.
2. Discussion of the Prior Art
In conventional dishwashing machines of the commercial spray-type, hot wash water is drawn from a wash tank at the bottom of the washing chamber and supplied to upper and lower wash arms in the washing chamber by means of a circulation pump mounted to the wash tank. The hot wash water is sprayed by rotation of the wash arms over the racked dishes in the washing chamber and is circulated into the wash tank. Subsequently, fresh hot rinse water is further supplied to the wash arms and sprayed over the dishes therefrom. The hot rinse water is also circulated into the wash tank, and the rinse water excess in amount is drained through an overflow pipe in the wash tank. In conventional dishwashing machines of the domestic or houshold type, hot wash water is drawn from a wash tank at the bottom of the washing chamber and supplied to upper and lower wash arms in the washing chamber by means of a circulation pump mounted to the wash tank. After being sprayed over the racked dishes in the washing chamber, the hot wash water is circulated into and drained from the wash tank. Subsequently, fresh hot rinse water is supplied into the wash tank and is drawn from the wash tank to the wash arms by means of the circulation pump. After sprayed over the racked dishes, the hot rinse water is circulated into the wash tank.
In the dishwashing machine of the commercial spray-type, the hot wash water is contaminated by food soils and cooking oil released from the dishes at an initial stage of the washing operation and circulated into the wash tank. With the contaminated wash water, the food soils of the dishes become difficult to remove. Assuming that glasses have been placed in the washing chamber after washing of dishes soiled with curry, the glasses will be soiled with the contaminated wash water. At the initial stage of the washing operation, the dishes absorb the heat of wash water sprayed thereon to cause fall of the temperature of wash water circulated into the wash tank. As a result, the hot wash water may not be maintained at a proper temperature required for sanitarily washing the dishes. In the dishwashing machines of the domestic type, the contamination of the wash water can be avoided but the temperature of wash water in the wash tank falls below the proper temperature.